全文获取类型
收费全文 | 761篇 |
免费 | 7篇 |
专业分类
电工技术 | 13篇 |
化学工业 | 142篇 |
金属工艺 | 13篇 |
机械仪表 | 38篇 |
建筑科学 | 7篇 |
矿业工程 | 1篇 |
能源动力 | 17篇 |
轻工业 | 58篇 |
水利工程 | 2篇 |
无线电 | 77篇 |
一般工业技术 | 114篇 |
冶金工业 | 235篇 |
原子能技术 | 4篇 |
自动化技术 | 47篇 |
出版年
2022年 | 7篇 |
2021年 | 9篇 |
2020年 | 1篇 |
2018年 | 2篇 |
2017年 | 7篇 |
2016年 | 11篇 |
2015年 | 5篇 |
2014年 | 9篇 |
2013年 | 22篇 |
2012年 | 15篇 |
2011年 | 14篇 |
2010年 | 9篇 |
2009年 | 23篇 |
2008年 | 21篇 |
2007年 | 21篇 |
2006年 | 20篇 |
2005年 | 23篇 |
2004年 | 22篇 |
2003年 | 27篇 |
2002年 | 25篇 |
2001年 | 8篇 |
2000年 | 19篇 |
1999年 | 15篇 |
1998年 | 102篇 |
1997年 | 46篇 |
1996年 | 31篇 |
1995年 | 20篇 |
1994年 | 21篇 |
1993年 | 22篇 |
1992年 | 14篇 |
1991年 | 18篇 |
1990年 | 17篇 |
1989年 | 9篇 |
1988年 | 11篇 |
1987年 | 5篇 |
1986年 | 11篇 |
1985年 | 17篇 |
1984年 | 6篇 |
1983年 | 12篇 |
1982年 | 6篇 |
1981年 | 10篇 |
1980年 | 9篇 |
1979年 | 4篇 |
1978年 | 3篇 |
1977年 | 16篇 |
1976年 | 16篇 |
1975年 | 3篇 |
1974年 | 2篇 |
1973年 | 2篇 |
排序方式: 共有768条查询结果,搜索用时 31 毫秒
21.
22.
Takuro Tomita Ayahito Uetake Tsutomu Asahina Kentaro Kayanuma Akihiro Murayama Yasuo Oka 《Journal of Superconductivity and Novel Magnetism》2005,18(3):405-410
Spin injection processes in the double quantum dots of ZnSe-based diluted magnetic semiconductors are discussed. Double quantum
dots are fabricated from ZnSe-based double quantum wells by electron beam lithography and wet etching. In these samples, the
photo-excited carriers in the magnetic dots are injected into the non-magnetic dots. The circular polarization degrees of
photoluminescence from the non-magnetic dots are measured by micro-photoluminescence measurement system under the magnetic
field up to 5 T. The maximum spin polarization degrees of injected carriers determined from our experiment are 10% for double
quantum wells and 15% for double quantum dots. The spin injection efficiency was estimated both from the observed circular
polarization degree and the diffusion length of carriers. We concluded that the spin injection efficiency is increased in
the double quantum dots. 相似文献
23.
25 mol% Y3+-doped BaCeO3 (BCY25) showed an extremely low activation energy of 0.3 eV for proton conduction at the surface. The resulting overall conductivity at the surface reached 8.24 × 10–3 S cm–1 at 400°C, which was 3, 8, and 28 times higher than those in the bulk of BCY25, 20 mol% Sm3+-doped ceria, and 8 mol% yttria-stabilized zirconia, respectively. Such fast proton conduction enabled an air/fuel (A/F ) sensor using BCY25 as the solid electrolyte to work above 150°C for H2 and above 250°C for C2H4. 相似文献
24.
A constitutive equation taking into account corner formation on the yield surface and the Bauschinger effect is developed. The behaviour of circular long tubes subjected to external pressure and axial load under plane strain and generalized plane-strain conditions are analyzed in conjunction with the proposed constitutive equation. The influence of axial load, the Bauschinger effect and corner formation, including the corner angle, and the mobility of the corner axis to the direction of stress history upon such global deformation behaviour as maximum pressure, pressure vs displacement relation and axial strain, are clarified. With regard to local deformation, these effects on the strain rate and strain localization, surface unevenness and shear band formation from the highly strained internal surface are investigated. 相似文献
25.
Y. Tomita 《International Journal of Mechanical Sciences》1982,24(12):711-716
In order to predict the influence of change in parameters in the constitutive equation upon deformation behaviour, a rigid plastic finite element perturbation method is developed. The change of such field variables as velocity, pressure, forming force and so on are expressed in terms of a power series of the perturbation of the parameters. The coefficients of the series are determined by solving the rigid plastic finite element perturbation equations. Several examples are presented to illustrate the advantages of using the proposed method to solve specific problems in preference to the conventional rigid plastic finite element method. 相似文献
26.
27.
Md Tasyrif Abdul Rahman Nobuyuki KawaharaKazuya Tsuboi Eiji Tomita 《International Journal of Hydrogen Energy》2014
In this work, spark-induced breakdown spectroscopy (SIBS) was employed to investigate the mixing process of a hydrogen jet in a constant-volume vessel. The local fuel concentration of the hydrogen jet was measured at several locations, using a SIBS sensor. A high-speed camera was used to visualize spark discharge fluctuations, and hydrogen jet concentration measurements were conducted simultaneously. Spectrally resolved atomic emissions from the plasma generated by the spark plug were examined to determine the local equivalence ratio. Direct visualization of the spark discharge provided useful information about the influence of spark discharge characteristics related to the spark timing. Using the developed SIBS sensor, atomic emission spectra were obtained from hydrogen Hα at 656 nm and nitrogen N (I) at 501 nm. Comparison of the intensity peaks of atomic emissions from hydrogen and nitrogen allows the local hydrogen concentration in a measured volume to be determined, and hence also the local equivalence ratio. The measurement results demonstrate the local variation in the equivalence ratio throughout the jet and along its axis. From the results, the spatial structure of the hydrogen jet affects the hydrogen/nitrogen mixing and could be clarified with SIBS technique when the spark is discharged. 相似文献
28.
Atsushi Okuro Hiroyuki Tomita Tsutomu Hihara 《International journal of remote sensing》2014,35(14):5394-5410
In this study, eight global sea surface temperature (SST) products for 2009 are compared to clarify their characteristics. The median of eight daily values, the Ensemble Median as Reference Product (EMRP), is used as a reference product for inter-comparison. The results show that the absolute value of mean differences and the value of root mean square (RMS) differences are higher in single-microwave products such as Advanced Microwave Scanning Radiometer for the Earth observing system (AMSR-E), Tropical Rainfall Measuring Mission Microwave Imager (TMI), and WindSat, than in products such as MicroWave Optimally Interpolated SST (MWOI), Merged satellite and in situ data Global Daily SST (MGD), and Operational Sea Surface Temperature and Sea Ice Analysis (OSTIA) constructed by merging several SST data. It is of note that the characteristics of SST products depend on the type of SST used within the product, rather than the data source used. A comparison of SST products was also conducted using EMRP and data observed by moored buoys. The results show that only AMSR-E has a warm bias (+0.06°C) while other products have a cool bias (maximum value ?0.10°C). The RMS error of TMI is the highest (0.57°C), and that of EMRP the lowest (0.28°C). Furthermore, the temporal variability between the data in each SST product was compared to those observed by the Kuroshio Extension Observatory (KEO) buoy. Results show that the temporal variability of EMRP corresponds well to that of buoy data, and that the RMS error of EMRP is lower than that of the other SST products. 相似文献
29.
30.
Invert traps have been successfully used to collect sediments at convenient locations within the sewer network, where large volumes of solids can be stored. In the present study, experiments have been performed in 15 cm wide and 5 m long channel for the measurement of retention ratios of five different invert trap configurations (namely, rectangular, trapezoidal with one side vertical, trapezoidal, trapezoidal with rectangular base, rectangular with trapezoidal base) having top width of 32 cm and depth of 28 cm with slots of three different sizes (namely, 5, 9 and 15 cm) for the flow of seven different sediment types (namely, two types of sand, glass beads and four types of plastic beads) at different flow rates for each trap. The flow rates selected in present study cover entire range of flow rate expected in channels during dry weather flow and monsoon. Flow field and retention ratio predictions for each invert trap configuration have been carried out using CFD modeling with the help of FLUENT software using Renormalization Group (RNG) k–ε along with Discrete Phase Model (DPM). The simulation results are capable of showing particle trajectories, the effect of flow rate and trap geometry on the flow patterns, developed within the trap. Based on CFD modeling and experimental measurements, it is concluded that the invert trap having rectangular shape with trapezoidal base is the most efficient trap configuration with highest sediment retention ratio. 相似文献